I agree with snorkledorf. Kindle is hard coded to only allow http:// or https:// no matter what you do. However, there is a solution available in the kindle store. Someone created something called the Kindle Bug App Browser for viewing websites offline, using games from the internet offline, and using tools/apps such as calculators, a stopwatch, and other apps offline.
The kindle bug app browser uses the cache from the kindle's internet browser to view websites and do things offline. Just type "kindle bug app browser" in the kindle store and it will come up or click on one of the two links below. There are currently two versions available but the seller makes all versions/updates available to anyone that buys any of the versions.
kindle bug app browser - version 1
kindle bug app browser - version 2.3